Autopositive film and paper and emulsions therefor



United States Patent Ofifice 3,368,898 Patented Feb. 13', 1968 3,368,898 AUTOPOSlTIVE FILM AND PAPER AND EMULSIONS THEREFOR Daniel A. Nepela, Saratoga, Califi, assignor to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware N Drawing. Filed Oct. 17, 1963, Ser. No. 317,033 6 Claims. (Cl. 96-64) The present invention relates to improvements in autopositive films and emulsions therefor. More particularly, this application relates to photographic silver halide emulsions, especially X-ray emulsions, which are capable to form strong, direct positive images on first development.

Various films, papers and emulsions have been proposed by the prior art which permit the taking of photographs and the obtainment of a direct positive image in one development step. There is a particular need for this type of film and emulsion, particularly in the X-ray field although not limited thereto, whenever it is necessary or desirable to quickly obtain a positive image without going through the involved steps of first developing a negative, removing the negative silver image thus formed, reexposing the residual silver halide and then forming a positive image by a second development. A number of attempts have been made by the prior art, usually by complicated and involved emulsion making procedures to produce such direct positive images. However, most of these attempts met only with limited degrees of success.

It is therefore, an object of the present invention to produce an improved direct positive light-sensitive silver halide material which, on image-wire exposure, will produce with a single development a strong, direct positive image. Other objects will be apparent from the following description.

I have found that the addition of a small amount of phenylthiourea to a silver halide emulsion makes it possible to obtain an autopositive image after a single development step. Preferably, the phenylthiourea is dissolved first in an organic, crystalloidal solvent material, which is substantially water-insoluble, has a low molecular weight and a boiling point above about 175 C. Solvent materials of this type are described in United States Patent 2,322,027. Organic phosphate esters such as triphenyl phosphate and tricresyl phosphate are particularly preferred. The solution of phenylthiourea in the tricresyl phosphate is then dispersed in an aqueous solution of gelatin and the dispersion thus obtained is then added to a suitable gelatin silver halide emulsion, preferably a commercial high speed ammonia type medical -ray emulsion.

This emulsion is then coated on a suitable support such as paper, baryta paper or a subbed film base prepared from a cellulose ester, polystyrene, polycarbonate or a polyester, e.g., polyethylene terephthalate. The coated emulsion is then dried and exposed image-wise under a suitable image pattern. The light-sensitive papers or films can be used for ordinary photographic purposes, involving exposure with visible light or for X-ray photography. A suitable exposure with visible light can be made by using a 500 watt photoflood lamp (at 110 volts), the lamp being spaced, for example, at a distance of about 12 inches from the sheet and given a time exposure of about seconds. Exposure conditions, of course, will vary widely with the sensitivity of the emulsion.

After exposure, development is carried out in the conventional manner, using a conventional developer solution which is suitable for the particular emulsion chosen. All operations can be carried out in subdued daylight or artificial light.

The invention will be more fully understood by reference to specific examples.

EXAMPLE I Six hundred milligrams of phenylthiourea were first dissolved in about 30 milliliters of tricresyl phosphate. These amounts resulted in a 2% solution, but the concentration may vary from 0.5 to 5%, if desired. This solution was dispersed mechanically into 180 milliliters of a 6% gelatin solution in water. The concentration of phenylthiourea at this point was about 0.3% but may range from 0.1 to 1.0%. The gelatin solution, prior to this dispersion, may be prepared in any suitable manner, preferably by swelling the gelatin in cold water and subsequent gentle heat ing under stirring.

After dispersion as above, 175 cc. of the phenylthiourea dispersion in the aqueous gelatin solution containing the phenylthiourea is added to 1 kilogram of a high speed ammonia type medical X-ray emulsion. The preparation of emulsions of this type is well known to persons skilled in the art and described, for instance, on page 168 of Bakers Photographic Emulsion Technique. The emulsion used in this experiment contained about grams of gelatin per kilogram of liquid emulsion and about 75 grams of silver halide, predominantly silver bromide with less than 3% of silver iodide, the latter percentage based on the total weight of silver halide in the emulsion. The final concentration of the phenylthiourea in the emulsion before the latter is applied to 'a support, which was about 0.04%, but may range from 0.01 to 0.1% based on the total weight of the liquid emulsion.

The emulsion was coated onto a transparent cellulose ester film base in such a manner that 200 milliliters covered an area of about square centimeters. The amount of phenylthiourea present in this area of 100 square centimeters was about 85 milligrams but may range from 20 to 210 milligrams.

After coating the support with the finished emulsion, the film was exposed for 10 seconds through a positive transparency with a 500 watt reflector photofiood lamp at volts, placed at a distance of 12 inches fromthe sheet.

Development was carried out in a suitable commercial developer such as Ansco Paper and Film Developer -l25 or Ansco X-ray developer A-30. Ansco A- developer has the following formula:

p-Methylaminophenol sulfate (Metol) grams 3 Sodium sulfite (anhydrous) do 44 Hydroquinone do 12 Sodium carbonate (monohydrate) do 65 Potassium bromide do 2 Water to make liters 2 Ansco X-ray developer A-30 has the approximate formula:

p-Methylaminophenol sulfate grams 3.5 Sodium sulfite (anhydrous) do 60 Hydroquinone do 9 Sodium carbonate (monohydrated) do 40 Potassium bromide do 2 Water to make liter 1 3 phenylthiourea yielded a very weak positive image, which was possibly induced by solarization.

EXAMPLE II To one kilogram of a commercial high speed ammonia type medical X-ray emulsion, of the kind described in Example I, was added grams of the magenta color former l-phenyl-3-heptadecyl-5-pyrazolone 4 sulfonic acid, and 87 cc. of the phenylthiourea gelatin dispersion described in Example I. The emulsion was then coated and exposed through a positive transparency as described in Example I. In place of the above color former, other color formers fast to diffusion and capable of reacting with the oxidation products of an aromatic primary amino developing agent to form magenta, yellow or cyan colored quinoneimine, azomcthine or phenazonium dye images can be used in place of the above-identified color formers and are described for instance, in United States Patent 2,733,143.

After exposure the film was developed in an N,N-dialkyl-p-phenylenediamine developer. The developer had the following formula:

1-amino-4-diethylaminobenzene hydrochloride gms 2 Sodium sulfite (anhydrous) do 2 Sodium carbonate (monohydrate) do 20 Potassium bromide do 2 Water to make liters 1 The pH of this developer was adjusted to 12.0 by the addition of sodium hydroxide. The developed film was bleached in a suitable alkali metal ferricyanide bleach solution, washed, fixed and washed. A magenta colored positive dye image was obtained.

EXAMPLE III Hydroquinone grams 5.0 Sodium sulfite (anhydrous) do 0.5 Sodium carbonate (monohydrate) do 100 Water to make 1iters 1 The developed plate was then treated with a conventional short stop solution of dilute acetic acid. The undeveloped, unhardened emulsion was then washed off with warm tap water having a temperature of about 50 to 60 C.

From the foregoing it will be understood that the invention contemplates the use of phenylthiourea, dissolved in a suitable organic solvent, the organic solution then be- 4 ing dispersed in a gelatin solution and thereafter combined with a silver halide emulsion.

It will be understood that various modifications, differing from those shown by the examples, may be made in the emulsion and the ingredients thereof. The emulsion may be applied to other suitable supports, depending upon the purpose for which the emulsion is used. The coating of the emulsion on the support is made in a conventional manner and with conventional equipment.

It Will also be understood that modifications such as would occur to those skilled in the art may be made in the composition and in its use without departing from the spirit and purpose of the invention. It is intended, therefore, by the claims which follow, to cover such modifications as far as the prior art properly permits.

I claim:

1. A photographic element carrying on a suitable support a light-sensitive gelatin silver halide emulsion having dispersed therein an amount of phenylthiourea ranging from 20 to 210 milligrams per square centimeters of coated area.

2. A liquid light-sensitive photographic silver halide emulsion having dispersed therein from 0.01 to 0.1% of phenylthiourea based on the total weight of the liquid emulsion.

3. A photographic emulsion according to claim 1 wherein said silver halide is silver bromide.

4. A photographic element comprising a suitable support carrying an ammonia type X-ray silver bromide emulsion having dispersed therein phenylthiourea in a reversal development accelerating amount.

5. A method of producing strong, direct positive X-ray photographs which comprises dispersing in an ammonia type silver halide emulsion a small amount of phenylthiourea, coating said emulsion on a support, image-wise exposing said emulsion through a pattern, developing and fixing the exposed emulsion.

6. A photographic element according to claim 1 wherein said emulsion contains a color former fast to diffusion capable of reacting with the oxidation products of an aromatic primary amino developing agent to form a colored dye image of the class consisting of azomethine, quinoneimin and phenazonium dyes.

References Cited UNITED STATES PATENTS 2,293,261 8/1942 Kendall 96-101 3,031,301 4/1962 Agens 96-10l 2,159,466 5/1939 Wilmanns et al. 96-59 3,155,507 11/1964 Blake 96-59 NORMAN G. TORCHIN, Primary Examiner.

J. TRAVIS BROWN, Examiner.

Disclaimer 3,368,898.Danie1 A. Nepela, Saratoga, Calif. AUTOPOSITIVE FILM AND PAPER AND EMULSIONS THEREFOR. Patent dated Feb. 13,

1968. Disclaimer filed Sept. 30, 1982, by the assignee, Eastman Kodak Co.

Hereby enters this disclaimer to all claims of said patent. [Oflicial Gazette February 8, 1983.] 

5. A METHOD OF PRODUCING STRONG, DIRECT POSITIVE X-RAY PHOTOGRAPHS WHICH COMPRISES DISPERSING IN AN AMMONIA TYPE SILVER HALIDE EMULSION A SMALL AMOUNT OF PHENYLTHIOUREA, COATING SAID EMULSION ON A SUPPORT, IMAGE-WISE EXPOSING SAID EMULSION THROUGH A PATTERN, DEVELOPING AND FIXING THE EXPOSED EMULSION. 